DESCRIPTION: (Applicant's abstract) There is mounting evidence that reactive oxygen intermediates (R0Is) my play a role in the etiology of Alzheimer's disease (AD). Although there are several endogenous sources of ROIs implicated in AD pathogenesis, this proposal will focus on ROIs produced due to mitochondrial dysfunction. To model this in tissue culture, we will used "cybrid" human neuroblastoma cells whose endogenous mitochondria have been replaced with mitochondria from patients with AD or matched controls. This proposal will address how the elevated levels of ROIs in AD cybrids affects cholinergic G-protein- coupled phosphoinositide (PI) signaling, protein kinase C (PKC) and extracellular signal regulated protein kinase (ERK) tyrosine phosphorylation and activation and transcription factor DNA binding. Our main hypothesis are that elevated ROIs will increase PKC and ERK tyrosine phosphorylation and activity and transcription factor activity and will attenuate responses to cholinergic receptor stimulation. Furthermore, AD cybrids will demonstrate increased sensitivity to the addition of oxidants and antioxidants compared with control cybrids. These studies will yield a clearer understanding of the effects of ROIs on signaling systems which may model critical alterations associated with AD.